The present invention relates to an alarm apparatus for alarming a driver of a vehicle and a method of alarming the same. More particularly, it relates to an alarm apparatus by which the driver of the vehicle is alarmed to his unusual situation with respect to a distance between the vehicle and the one in front. Note, in this specification, the above distance between the vehicle and the one in front may be referred as "inter-vehicle distance", hereinafter.
Conventional art includes an alarm apparatus which automatically detects a distance between a driver's vehicle and the one ahead traveling on the same traffic lane as the preceding vehicle travels by a vehicle radar equipment, establishes a minimum permissible distance from relationships among a vehicle speed, a relative speed between the vehicle and the one ahead and the distance therebetween so as to prevent the vehicle from approaching the preceding vehicle up to a distance required for avoiding the vehicles' collision, and displays a warning or activates an alarm buzzer when the distance between the driver's vehicle and the one ahead reaches the minimum permissible distance.
The above-mentioned conventional art alarm apparatus includes a radar unit for automatically detecting a distance between the driver's vehicle and an object in front, and an alarm-output judging unit which judges whether the distance between the vehicle and the preceding vehicle is within the minimum permissible distance on the basis of a vehicle speed and the distance data obtained by the radar unit and which generates a warning signal if the above judgement is "yes" (within the minimum permissible distance ). The alarm apparatus further includes a display unit which inputs the warning signal from the alarm judging unit to carry out displaying of caution/warning, the accompanying alarm buzzer, a switch for activating or inactivating the alarm apparatus and a vehicle speed sensor for detecting a velocity of the vehicle for the alarm-output judging unit.
In the above-mentioned alarm apparatus, the alarm display and the alarm sound are generated in accordance with the detected "inter-vehicle" distance between the vehicle and the preceding vehicle, the relative velocity therebetween and the velocity of the driver's vehicle, irrespective of conditions of the driver.
Meanwhile, it often happens that the driver temporarily drives the vehicle without paying attention to the forward of the vehicle since he/she manipulates various switches of audio/visual instruments, an air conditioner etc. installed at a center (e.g. a front center console) of an instrument board or he moves his eyes from the front into display panels of the instruments in order to confirm the operating states of the instruments. Under such a driver's condition and if the inter-vehicle distance alarm display or sound is generated, then the driver upon hearing the warning sound moves his eyes ahead in order to confirm the front of the vehicle and thereafter, he begins to brake the vehicle after judging the vehicle is approaching the preceding object (vehicle) too close. Under such a situation, therefore, when the alarm distance is established too short, the driver will have little time required for preventing the collision. Conversely, when the long alarm distance is established upon taking such a situation into consideration, there is a possibility that when the driver drives the vehicle while gazing ahead with care, the alarm sound is made in spite of a sufficient inter-vehicle distance. In such a case, the resulting alarm sound would give the driver a sense of incompatibility or burden.